docs: def get_files_from_textfile(textfile_handler):
      """Yield the file names and widths by parsing a text file handler."""
      for line in textfile_handler:
          line = line.rstrip()
          try:
              (image_name, width) = line.rsplit(',', 1)
              width = int(width)
          except ValueError:
              image_name = line
              width = None
          yield (image_name, width)